Integrated passive magnetic bearing system and spindle permanent magnet for use in a spindle motor

Abstract

An apparatus for rotatably journaling a rotor of a spindle motor about a stator comprising a plurality of magnetic bearings for use in a disc drive including an annular ring single-pole magnet which is integral with the spindle permanent magnet of a spindle motor rotor assembly and disposed in opposition to a complementary annular magnet ring attached to the stator assembly of the spindle motor. These magnetic bearings in conjunction with an axial pivot form a radially stable bearing system for maintaining rotor displacement about the stator in conjunction with a conventional axial pivot. The present invention provides for the unique combination of magnetic bearings with other conventional pivots for use in disc drive systems.

What is claimed is: 
     
       1. In a disc drive having a spindle motor assembly comprised of a spindle permanent magnet held in opposition to an electromagnet assembly, an apparatus for journaling a rotor about a stator in a spindle motor of a disc drive comprising: a shaft centrally disposed on said rotor;   a reservoir in said stator for receiving said shaft;   bearing means comprising a hydrodynamic bearing for maintaining radial stiffness of said rotor with respect to said stator while said bearing means is operational; and   alignment means for centering said rotor about said stator during non-operational periods, said alignment means comprising a magnetic bearing having one pole integral to said spindle permanent magnet.   
     
     
       2. The apparatus of claim 1 wherein said alignment means comprises: a first annular disc, said disc comprising an axially aligned magnetic pole, said disc radially extending from said stator; and   a spindle permanent magnet having a first and second end and non-magnetized region disposed there between, said first end comprising a plurality of magnetic poles disposed on said rotor in opposition to said spindle motor electromagnet assembly, said second end comprised of a like axially aligned magnetic pole disposed on said rotor and opposing said axially aligned magnetic pole on said first annular disc.   
     
     
       3. The apparatus of claim 2 wherein said first annular disc is disposed 0.25 mm beneath said axially magnetized region. 
     
     
       4. The apparatus of claim 1 wherein said first annular disc further comprises an annular shaped magnetic permeable spacer region disposed between said plurality of axially aligned magnetic poles and said stator, said magnetic permeable spacer region providing a magnetic flux return for increasing efficiency of the magnetic bearing.